The water holding capacity is the highest in clayey soil

Preventions of soil pollution can be done by
(i) using manures instead of synthetic fertilisers.
(ii) using natural pesticides.
(iii) avoiding dumping of polythene and plastics in soil.
(iv) treating industrial waste before releasing it in the soil.
Preventions of soil erosion can be done by
(i) afforestation that is large scale planting in placee cut down forests.
(ii) avoiding overgrazing of grasslands.
(iii) terrace farming and other better farming methods in hilly areas.

Given, Time = 40 mins
Volume of water = 200 mL
So, rate of percolation
\(\frac { amount\quad of\quad water(mL) }{ percolation\quad time(min) } =\frac { 200 }{ 40 } =5mL/min\)
Therefore, percolation rate of water = 5 mL/min

Labelled sketch of the cross-section of soil is

Differences between clayey soil and sandy soil are

Clayey soil has an important characteristic. It can retain water and moisture and are rich in humus. Therefore, it is suitable for growing cereals like wheat, gram and paddy.

Soil formation is a slow process which occurs in following two steps
(i) Weathering of rocks is the breakdown of rocks into small particles by the action of air, wind and water.
(ii) These small particles mix with humus (organic matter) and form soil.

Weathering is a natural process by which huge rock is broken down into tiny particles but at a very slow rate.

When dry soil is added in the water in a glass and stir it, bubbles appear. These bubbles are caused due to the air present in between the soil particles

The absorption percentage of water can be calculated by the formula given below
Percentage of water absorb
\(\frac { amount\quad of\quad water\quad absorted(in\quad ml) }{ amount\quad of\quad soil(in\quad gm) } x100\)

Clayey soil absorbs more water but allows less water to percolate

Loamy soil is the most fertile soil and used for growing crops.

The soil has been categorised into four major groups, i.e.
(i) clay
(ii) silt
(iii) sand
(iv) gravel

The moisture content of the soil can be calculated by the formula as follows
= \(\frac { mass\quad of\quad water\quad in\quad soil }{ original\quad mass\quad of\quad soil } \times 100\)
Given, Original mass of soil = 200 g
Mass of soil after drying = 170 g
Then mass of water in soil will
= 200 - 170 = 30 g
The percentage of water in soil will be
\(\frac { 30g }{ 200g } \times 100=15%\)
 

Raw soil differs from baked soil. The raw soil is white or dull blackish coloured soil. It contains water and air in it and can be moulded.
Baked soil is the heated raw soil which lost its water molecule due to heating and becomes red. Once the soil gets heated, it cannot be moulded into other form. Clay soil is used for making matkas, toys, pots, etc. The soil is kneaded along with horse dung to make best quality of raw clay soil. This kneaded soil is then placed on the wheel and appropriate shape is given. The final shape of the material is given with hands. The pots and matkas are then kept for drying for three days. These items are baked at high temperature after drying in air and then coloured.

Ans. Yes, soil erosion does not occur easily where the land is covered by vegetation (trees and other plants). It occurs easily in those areas of land which are not covered by vegetation (trees and other plants) or have very little vegetation. If there is vegetation on land,
(i) then the roots of vegetation growing in the soil bind the particles of topsoil firmly. Due to this, the blowing wind and flowing rainwater are not able to carry away topsoil and hence soil erosion does not occur.
(ii) then much of the falling rain hits the trees and plants before it hits the soil. In this way, the cover of vegetation softens the effect of heavy rains on the soil